Self-expanding stent delivery system

ABSTRACT

A stent delivery system delivers a self-expanding stent to a predetermined location in a body lumen. The delivery system has a catheter body, a retractable outer sheath and a proximal retraction handle connected to a proximal end of the catheter body. The catheter body carries the stent near a distal end of the catheter body for transporting the stent for deployment. The sheath surrounds and contains the stent in a delivery configuration where the stent has a reduced radius along its entire axial length. The sheath has an outer tube a separate inner tube. The outer tube has a distal end portion surrounding the stent along its entire length and a proximal end portion connected to the retraction handle. The inner tube is disposed concentrically within the outer tube and has a distal end portion surrounding the stent only along a part of its entire length.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a self-expanding stentdelivery system for delivering a self-expanding stent.

2. Background Information

Delivery systems for deploying endovascular stent grafts, self-expandingstents or balloon expandable stents are well-known in the field ofmedical technology. One example of a stent delivery system fordelivering a self-expanding stent is disclosed in International PatentPublication No. WO 98/23241, which corresponds to U.S. Pat. No.5,968,052.

As has been explained in the before-mentioned citation a self-expandingstent is a stent which expands from a compressed delivery position toits original diameter when released from the delivery device, exertingradial force on the constricted portion of the body lumen tore-establish patency. One common self-expanding stent is manufactured ofnitinol, a nickel-titanium shape memory alloy, which can be formed andannealed, deformed at a low temperature, and recalled to its originalshape with heating, such as when deployed at body temperature in thebody.

One important factor in delivering the stent is a controlled preciseretraction of the retractable outer sheath. What is needed is a deliverysystem which provides for a controlled and precise retraction of theretractable outer sheath and enabled the physician to accuratelydetermine proper positioning of the stent, as well as track theretraction of the outer sheath.

Known delivery systems suffer, however, from the draw-back that theretraction forces are often too high, especially in cases where thestents are covered with layers made from body-compatible materials orthe like so that the friction forces between the stent and the outersheath may become excessively high.

In view of the above, it will be apparent to those skilled in the artfrom this disclosure that there exists a need for an improvedself-expanding stent delivery system for delivering a self-expandingstent. This invention addresses this need in the art as well as otherneeds, which will become apparent to those skilled in the art from thisdisclosure.

SUMMARY OF THE INVENTION

Therefore one object underlying the present invention is to provide aself-expanding stent delivery system for delivering a self-expandingstent that is able to overcome the before-mentioned draw-back so that asmooth retraction of the retractable outer sheath is possible.

Basically, the above object is attained by providing a self-expandingstent delivery system according to the present invention that comprisesa retractable outer sheath that is divided into an outer tube and aseparate inner tube. The tubes are disposed concentrically with respectto each other. The outer tube surrounds and covers the stent along itsentire length whilst the separate inner tube surrounds the stent onlypartly, as especially only along about 50% of its entire length.

This simple and effective arrangement results in the advantage that thesurface between the stent and the outer sheath is reduced by aremarkable percentage, especially up to 50%, so that the retractionforces become significantly smaller.

A specifically advantageous embodiment provides for an arrangement ofstop members. One of the stop members can be disposed at the distal endof a retraction tube of the retraction handle whilst the second stopmember is disposed at the proximal end portion of the inner tube. So,upon operation of the retraction handle the outer tube is retracted andafter a predetermined length of retraction the stop members engage eachother so that also the inner tube can be retracted upon only oneoperation of the retraction handle so that the physician can deploy thestent with the same kind of operation as with conventional deliverysystems but much smoother and with lower retraction forces. Thisfacilitates an exact position of the stent as the stent is preventedfrom being longitudinally compressed.

According to the present invention, the outer tube may be a co-extrudedtubing, e.g., made from polyamid whilst the inner tubing is preferablymade from polyethylene.

In general, the materials of the tubes are to be chosen fromcombinations of materials that result in low friction resistance.Alternatively, the materials of the tubes are tubings comprising layerswith low friction coefficients.

These and other objects, features, aspects and advantages of the presentinvention will become apparent to those skilled in the art from thefollowing detailed description, which, taken in conjunction with theannexed drawings, discloses a preferred embodiment of the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the attached drawings which form a part of thisoriginal disclosure:

FIG. 1 is a schematically simplified side cross sectional view of adistal end portion of a self-expanding stent delivery system accordingto a first embodiment of the present invention;

FIG. 2 is a schematically simplified side cross sectional view of aproximal end portion of the self-expanding stent delivery systemillustrated in FIG. 1 according to the present invention; and

FIG. 3 is a schematically simplified side cross sectional view, similarto FIG. 1, of a distal end portion of a self-expanding stent deliverysystem of a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Selected embodiments of the present invention will now be explained withreference to the drawings. It will be apparent to those skilled in theart from this disclosure that the following descriptions of theembodiments of the present invention are provided for illustration onlyand not for the purpose of limiting the invention as defined by theappended claims and their equivalents.

Referring initially to FIGS. 1 and 2, a self-expanding stent deliverysystem 1 is illustrated in accordance with a first embodiment of thepresent invention. The delivery system 1 is intended for delivering aself-expanding stent 2 shown in elevation in FIG. 1.

The delivery system 1 basically comprises a catheter body 3 having aproximal end 5 and a distal end 4. The catheter body 3 is adapted totransport the stent 2 to a predetermined site in a body lumen fordeployment that is not shown in FIGS. 1 and 2.

The catheter body 3, furthermore, comprises a metal and/or ametal-polymeric and/or a polymeric shaft 18 that extends from theproximal end 5 to the distal end 4.

The delivery system 1, furthermore, comprises a retractable outer sheath6 shown in FIGS. 1 and 2 that surrounds the stent 2 and contains thestent 2 in a delivery configuration where the stent 2 has a reducedradius along its entire length L_(E) shown in FIG. 1.

FIG. 2 shows a proximal retraction handle 7 that may be configured as anintegral part of a so-called Tuohy Borst valve. The handle 7 is disposedat the proximal end 5 of the catheter body 3 as shown in FIG. 2.

According to the present invention the sheath 6 is a combination of anouter tube 8 and a separate inner tube 11. The outer tube 8 has a distalend portion 9 that surrounds the stent 2 along its entire length L_(E)as can be learned from FIG. 1.

The outer tube 8, furthermore, comprises a proximal end portion 10 beingconnected to the retraction handle 7, e.g., by an adhesive connection.

The separate inner tube 11 is disposed concentrically within the outertube 8 and concentrically surrounds the metal shaft 18 of the catheterbody 3. The inner tube 11 comprises a distal end portion 12 surroundingthe stent 2 only along a part L_(P) of its entire length L_(E) as can beseen form FIG. 1. This configuration significantly reduces the frictionforces between the stent 2 and the outer sheath 6 so that the forces forretraction of the outer sheath 6 become remarkably smaller in comparisonto conventional delivery systems.

The handle 7 of the preferred embodiment shown in FIGS. 1 and 2comprises a retraction tube 13 that is connected at its distal end 14 tothe proximal end portion 10 of the outer tube 8. The retraction tube 13comprises a stop member 15 at its distal end 14 (see FIG. 2). The stopmember 15 can be configured as an annular ring extending inwardly fromthe inner periphery of the retraction tube 13.

As can be seen from FIG. 2 the retraction tube 13 concentricallysurrounds the proximal end portion 5 of the catheter body 3 and theproximal end portion 16 of the inner tube 11.

The inner tube 11, in turn, comprises a stop member 17 at its proximalend portion 16. The stop member 17 is alternately configured as anannular ring extending outwardly from the outer periphery of the innertube 11.

As can be seen from FIG. 2, the stop members 15 and 17 are adapted to beengaged with one another upon retraction of the handle 7. When operatingthe retraction tube 13 of the handle 7 in the direction of arrow A inFIG. 2, the outer tube 8 is pulled back in the direction of arrow Bshown in FIG. 1 to slide partly on the inner tube 11 as the inner tube11 covers only a part of the stent 2. Upon engagement of the stopmembers 15 and 17, the inner tube 11 is also pulled back in thedirection of arrow B shown in FIG. 1 so that stent 2 can be released anddeployed at a predetermined site in a body lumen.

SECOND EMBODIMENT

FIG. 3 depicts a second embodiment of a delivery system 1 according tothe present invention. In view of the similarity between the first andsecond embodiments, the parts of the second embodiment that areidentical or similar to the parts of the first embodiment will be giventhe same reference numerals as the parts of the first embodiment.Moreover, the descriptions of the parts of the second embodiment thatare identical or similar to the parts of the first embodiment of FIGS. 1and 2 may be omitted for the sake of brevity. Also, the proximal endportion illustrated in FIG. 2 is used with of the self-expanding stentdelivery system of this second embodiment with slight modifications toaccommodate the differences between the first and second embodiments.

The basic difference between the embodiments of FIGS. 1 and 3 is to beseen in the fact that the inner tube 11 is fixed at a fixing portion 19to the shaft 18 shortly after the stent 2 as seen in the direction ofarrows X and Y. To retract inner tube 11, with this embodiment, it ispossible to retract the shaft 18 after having retracted the outer tube8.

The terms of degree such as “substantially”, “about” and “approximately”as used herein mean a reasonable amount of deviation of the modifiedterm such that the end result is not significantly changed. For example,these terms can be construed as including a deviation of at least ±5% ofthe modified term if this deviation would not negate the meaning of theword it modifies.

This application claims priority to European Patent Application No. 02020 10.3 filed on Sep. 9, 2002. The entire disclosure of European PatentApplication No. 02 020 10.3 is hereby incorporated herein by reference.

While only selected embodiments have been chosen to illustrate thepresent invention, it will be apparent to those skilled in the art fromthis disclosure that various changes and modifications can be madeherein without departing from the scope of the invention as defined inthe appended claims. Furthermore, the foregoing descriptions of theembodiments according to the present invention are provided forillustration only, and not for the purpose of limiting the invention asdefined by the appended claims and their equivalents. Thus, the scope ofthe invention is not limited to the disclosed embodiments.

1. A self-expanding stent delivery system for delivering aself-expanding stent to a predetermined location in a body lumen, theself-expanding stent delivery system comprising: a catheter body havinga proximal end and a distal end, the catheter body being configured andarranged to carry the stent near the distal end of the catheter body fortransporting the stent to the predetermined location in the body lumenfor deployment; a retractable outer sheath configured and arranged tosurround the stent and contain the stent in a delivery configurationsuch that the stent has a reduced radius along its entire axial length;and a proximal retraction handle connected to the proximal end of thecatheter body, the retractable outer sheath comprising, an outer tubehaving a distal end portion configured and arranged to surround thestent along the entire length of the stent and further having a proximalend portion connected to the retraction handle, and a separate innertube disposed concentrically within the outer tube and having a distalend portion configured and arranged to surround the stent only along aproximal part of the entire length of the stent, the inner tube having aproximal end portion housed in the retraction handle, retraction of thehandle causing the distal end portion of the outer tube to recede fromthe stent and from the distal end portion of the inner tube.
 2. Theself-expanding stent delivery system according to claim 1, wherein thehandle comprises a retraction tube connected at its distal end to theproximal end portion of the outer tube.
 3. The self-expanding stentdelivery system according to claim 2, wherein the retraction tubecomprises a stop member at its distal end.
 4. The self-expanding stentdelivery system according to claim 3, wherein the retraction tubeconcentrically surrounds the proximal end of the catheter body and aproximal end portion of the inner tube.
 5. The self-expanding stentdelivery system according to claim 2, wherein the retraction tubeconcentrically surrounds the proximal end of the catheter body and aproximal end portion of the inner tube.
 6. The self-expanding stentdelivery system according to claim 5, wherein the inner tube comprises astop member at its proximal end portion that is adapted to be engagedwith the stop member of the retraction tube upon the retraction of thehandle.
 7. The self-expanding stent delivery system according to claim6; wherein the inner tube surrounds the stent along about 40% to 60% ofthe entire length of the stent.
 8. The self-expanding stent deliverysystem according to claim 1, wherein the inner tube surrounds the stentalong about 40% to 60% of the entire length of the stent.
 9. Theself-expanding stent delivery system according to of claim 1, whereinthe stent is configured as a stent graft or a covered stent.
 10. Theself-expanding stent delivery system according to claim 1,wherein theseparate inner tube is fixed to a shaft of the catheter body.
 11. Aself-expanding stent delivery system comprising: a self-expanding stent;a catheter body having a shaft, a proximal end, and a distal end, thecatheter body being configured and arranged to carry the stent near thedistal end of the catheter body for transporting the stent to apredetermined site in a body lumen for deployment; a retractable outersheath configured and arranged to surround the stent and contain thestent in a delivery configuration such that the stent has a reducedradius along its entire axial length; and a proximal retraction handleconnected to the proximal end of the catheter body, the retractableouter sheath comprising, an outer tube having a distal end portionconfigured and arranged to surround the stent along the entire length ofthe stent and further having a proximal end portion connected to theretraction handle, and a separate inner tube disposed concentricallywithin the outer tube and having a distal end portion configured andarranged to surround the stent only along a proximal part of the entirelength of the stent, the inner tube having a proximal end portionaffixed to the shaft proximally of the stent, retraction of the handlecausing the distal end portion of the outer tube to recede from thestent and from the distal end portion of the inner tube.
 12. Theself-expanding stent delivery system according to of claim 11, whereinthe stent is configured as a stent graft or a covered stent.
 13. Theself-expanding stent delivery system according to claim 11, wherein thehandle comprises a retraction tube connected at its distal end to theproximal end portion of the outer tube.
 14. The self-expanding stentdelivery system according to claim 13, wherein the retraction tubecomprises a stop member at its distal end.
 15. The self-expanding stentdelivery system according to claim 13, wherein the retraction tubeconcentrically surrounds the proximal end of the catheter body and theproximal end portion of the inner tube.
 16. The self-expanding stentdelivery system according to claim 11, wherein the inner tube surroundsthe stent along about 40% to 60% of the entire length of the stent.